<!DOCTYPE html>
<html lang="en">

    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
    </head>

    <body>
        <textarea id="code">return "hi";</textarea>
        <button id="button">Run</button>
        <pre id="output"></pre>

        <script>
  // Your code here.
        </script>
    </body>

</html>